This SCR timer was found in an old English documentation. The SCR can be the TUIC106 and modern equivalent transistors like the BC557 for TR1 and BC547 for the others.
Found in na 1970 EDN this circuit has a parallel regulation providing a symmetrical output of 15 V....
This configuration found in a 1976 publication can be elaborated with more modern operational...
This ultra-simple meter uses an output transformer and a small speaker as a microphone. The...